Our studies take as their point of departure the hypothesis that identical manifest symptoms stem from a variety of underlying psychopathogenic processes and that, conversely, identical pathogenic processes and influences can give rise to a variety of symptoms. If this hypothesis can be substantiated it would follow that any belief in unvarying connections between surface manifestations and underlying psychopathogenic processes can lead to serious errors in determining the diagnostic status of presenting symptom pictures and, thereby, to serious prognostic error, and to inappropriate treatment and management. To test this hypothesis, we have drawn upon the Clinic's specialised resources and attempted to apply them to the symptomatic study of children presenting themselves for assessment and therapy where the latter is recommended and instituted. These resources include a psychoanalytic method of diagnostic assessment (the Provisional Developmental Diagnostic Profile); the systematic collection of data from psychoanalytic therapy which is made available to our studies through a detailed system of reporting; the categorisation of this material in the form of an Index which also allows data from closed cases to be used in the study; and the re-application of the Profile Assessment method at various stages of treatment which then permits comparison with earlier formulations, recommendations and predictions. These methods of study have been applied to various groups of childhood disturbances including those of food intake, of learning, of various forms of aggressive behavior, and of 'main-line' heroin addiction; and our studies to date, while preliminary, tend to support the hypothesis outlined above.